Ethanol for industrial use is conventionally produced from petrochemical feed stocks, such as oil, natural gas, or coal, from feed stock intermediates, such as syngas, or from starchy materials or cellulose materials, such as corn or sugar cane. Conventional methods for producing ethanol from petrochemical feed stocks, as well as from cellulose materials, include the acid-catalyzed hydration of ethylene, methanol homologation, direct alcohol synthesis, and Fischer-Tropsch synthesis. Instability in petrochemical feed stock prices contributes to fluctuations in the cost of conventionally produced ethanol, making the need for alternative sources of ethanol production all the greater when feed stock prices rise. Starchy materials, as well as cellulose material, are converted to ethanol by fermentation. However, fermentation is typically used for consumer production of ethanol, which is suitable for fuels or human consumption. In addition, fermentation of starchy or cellulose materials competes with food sources and places restraints on the amount of ethanol that can be produced for industrial use.
U.S. Pat. No. 5,017,731 describes a process for directly converting ethane to ethanol and methanol using controlled oxidation. The reaction takes place in an inert reactor, i.e., one having internal surfaces which do not affect the reaction, in the absence of a catalyst. The ethane is intimately mixed with air or oxygen prior to the introduction of the mixed gases into a heated pre-reactor which allows the pre-reaction or induction period to proceed. The pre-reacted gases then enter the reactor where the reaction takes place at elevated temperatures of 200° C. to 350° C. and at elevated pressure from 10 to 150 atmospheres. The percentage of oxygen in the mixture of reactant gases is kept below 15% by volume and is preferably 2 to 10% by volume.
U.S. Pat. No. 5,162,578 describes a process for producing acetic acid by a catalytic oxidation with oxygen of ethane, or ethylene, or mixtures thereof. Two different catalysts are used for the oxidative dehydrogenation of ethane and subsequent hydration of ethylene or oxidation of ethylene oxidation to acetic acid.
The need remains for processes for making ethanol from available industrial sources.